1. Field of the Invention
The present invention broadly relates to devices for expediting installation and removal of fittings in hard-to-reach locations and, more particularly, is concerned with a torque limiting collar for rigidly coupling a fitting to a stationary structure so as to substantially prevent transmission of damage-inducing torque through the fitting to conduit or tubing associated with it.
2. Description of the Prior Art
Fittings in tubular conduit or tubing which transfer fluid medium under pressure require application of torque to ensure that flare, O-ring, and other types of seals in the fittings are seated to prevent leakage. Current techniques require the use of a backing or counter-coupling wrench engaged on the stationary part of the fitting while torque is applied to the nut part of the fitting. It is imperative that no movement of the stationary fitting part be permitted or damage to the fitting and/or tubular conduit will likely result. Location of the fitting, adjacent space limitations, torque values to be achieved and skill in using the backing wrench are dependent variables which affect torque application and potential damage. Failure of either the fitting or conduit often results in expensive maintenance repairs and unscheduled aircraft/equipment downtime.
In the case of the Air Force's F-16 aircraft generator housing, two specific circumstances make proper application of torque to fittings a troublesome matter. First, the generator housing is fabricated from spun cast magnesium, consequently, virtually all transmission of torque to the housing through the fitting must be avoided, such as by skilled use of a backing wrench when tightening the fitting in order to prevent damage to the housing fitting or housing due to over-application of torque. Second, however, the location of the oil fittings are not conducive to effective application of a back-up wrench to them. As a result, a significant number of generator failures have been attributed to overheating due to loss of the cooling oil stemming from damaged fittings or a cracked housing thread boss.
Consequently, a need exists for a technique to ensure application of proper torque to tubular fittings while preventing transmission of damage-inducing torque through the fittings to adjacent housing or tubular structures.